In recent years it has become more and more common place to utilize breakerless ignition systems, of either the inductive or capacitor discharge type with small internal combustion engines, such as used on lawnmowers and chain saws. Because these applications generally require compact systems, it has been the trend to fabricate unitary ignition modules which encapsulate in the same housing both the ignition coil and the electronic control circuit. From the standpoint of economy and ease of fabrication, one ground terminal is invariably used. One such capacitor discharge ignition system (CDI) is disclosed in Burson U.S. Pat. No. 4,036,201 and another in Piteo U.S. Pat. No. 3,484,677 which discloses an inductive type system. In both these patents, assigned to the same assignee as the present application, the coils and the ignition circuit components are shown wired together and, as stated above, a single, common ground connection is employed. In recent installations, these systems have generally included a cut-off or "kill" switch, which when actuated will prevent the system from generation ignition pulses to sustain engine operation. This type of cut-off is usually accomplished by grounding out the primary coil or the charging coil in the CDI system.
To comply with newly enacted safety legislation, engine cut-off must occur in a very brief time interval after the operator's hands release the equipment controls. The concept is that if the operator slips or falls when handling potentially hazardous power equipment, the engine will not continue to run. Occasionally, with a conventional type of unitary module, if for any reason, a common ground terminal connection has broken away, the ignition system would continue to generate ignition pulses and the engine would not stop as required. Such failures of the cut-off mechanism results from the presence of wiring circuit connections within the coil module so that a complete and operative circuit still exists even though the ground connection has become disconnected.
It is the principal object of this invention to provide an ignition system cut-off which will not be rendered ineffective in the event of disconnection of the ground terminal.
It is another object of this invention to provide an ignition system in which a cut-off switch is connected to a first ground terminal and the primary coil and electrical control circuit are each separately connected to two discrete ground terminals, but are not otherwise interconnected.
It is a further object of this invention to provide an ignition system cut-off of the above type in which discrete terminals, each having an inner end in electrically conductive contact with electrically separated points in the module and an outer end, each affixed at spaced points to the core of the ignition system.